Okay, so I'll start the discussion, because every time we all get together, it turns to this anyway. And while I have no control over this situation, if anybody ever asked me - or if Nicole and Matt make it into the Legion of Super Animators (The 839 board) and have some sway over the discussion - this is what I think.
There are two types of writers in animation. Story board people, and script people. There are two types of productions in animation, board based story telling and script based story telling.
With that in mind, my little math here ONLY works within an 839 production, because those are the shows where story and script changes as the show evolves. On a prime-time script driven show, I do not believe that to be the case. (Correct me if I'm wrong.)
I think the hypothetical residuals should be split 80/20, depending on the production.
On a script show - lets say Fairly Oddparents or Yin Yang Yo - the script writer does all the heavy lifting for the story telling - from premise, to outline, to three drafts of the script. Because the script is the blueprint, acting, direction, setting, and visual gags are all laid in there. At this point, a board person will tell this story... but it's already been arc'd out.
On a board show - lets say Spongebob - a writer will write a detailed outline and then off the board artist goes. Here, I would switch it - give the board artist 80 percent of an imaginary residuals, and give the person who created the story and wrote the outline 20 percent.
And in a John K world where productions don't even have keyboards because script writing is unimportant, the storyboard artist could go from premise, to board, and keep 100% of any hypothetical residuals.
How the production worked would be created by the person who created the show, which only seems fair.
There's my brain dump. Have at it.